Vilazodone is the 5-5-{4-[(4-(5-Cyano-1H-indol-3-yl)butyl]-piperazin-1-yl}-benzofuran-2-carboxylate methyl molecule provided with molecular weight equal to 477.99.
From a pharmacological point of view, vilazodone is a selective serotonin reuptake inhibitor (SSRI) and a partial agonist of 5-HT1A receptors.
On account of this action thereof, vilazodone falls within the class of antidepressant drugs and finds application in the treatment of psychiatric diseases and in the treatment of major depressive syndrome (MDD) in particular.
Vilazodone and the preparation thereof were described, for example, in U.S. Pat. No. 5,532,241.
In particular two related routes of Vilazodone preparation are known.
The first synthesis route provides for the condensing of indol-5-carbonitrile with 4-chlorobutyrylchloride to give 3-(4-chlorobutyryl)-1H-indol-5-carbonitrile, which is reduced with diborane, to give 3-(4-chlorobutyl)-1H-indol-5-carbonitrile. The reaction of the latter compound with 5-(1-piperazinyl)benzofuran-2-carboxylic acid (V) leads to the expected 1,4-disubstituted piperazine 5-{4-[4-(5-cyano-1H-indol-3-yl)-4-hydroxy-butyl]-piperazin-1-yl}benzofuran-2-carboxylate methyl. Finally, the carboxyl group of the piperazine is converted into the carboxamide of interest by reaction with 2-chloro-1-methylpyridinium methanesulphonate (CMPM) and ammonia gas.
A second related synthesis route provided for hydrogenation of the 5-nitrobenzofuran-2-carboxylic acid ethyl ester with Raney nickel and H2 in MeOH to give the corresponding compound of 5-aminobenzofuran with bis(2-chloroethyl) amine in dichloromethane to give 5-(1-piperazinyl)-benzofuran-2-carboxylic acid ethyl ester. The reaction of the latter compound with di-tert-butyl dicarbonate in THF provides the protected amino compound 5-[4-(tert-butoxycarbonyl)-1-piperazinyl]benzofuran-2-carboxylic acid ethyl ester, which is first reacted with formamide and sodium alkoxide in N-methylpyrrolidone to provide the corresponding amide, and then deprotected by treatment with HCl/MeOH to give 5-(1-piperazinyl)benzofuran-2-carboxamide. Finally, this amide is condensed with 3-(4-chlorobutyl)-1H-indol-5-carbonitrile to give vilazodone.
Also known by Timo H. et al. in J. Med. Chem 2004, 47, 4684-4692 pp. 4684-4692 is a process for preparing vilazodone that provides for an initial phase in which indol-5-carbonitrile is condensed with 4-chlorobutyrylchloride to give 3-(4-chlorobutyryl)-1H-indol-5-carbonitrile, which is then reduced with sodium bis(2-methoxyethoxy)-aluminium hydride in toluene (vitride), to give 3-(4-chlorobutyl)-1H-indol-5-carbonitrile which is then reacted with 5-piperazin-1-yl-benzofuran-2-carboxylate hydrochloride to give the expected piperazine.
However, the use of a reducing agent such as vitride in the synthesis process makes it difficult to manage the production system and requires a series of precautions which make the process of the prior art hardly feasible and cost-effective from an industrial point of view. Furthermore, vitride is a particularly expensive reducing agent.
Currently, the increasing demand for vilazodone has resulted in a pressing need to avail of alternative processes for the preparation thereof.
One of the aims of the invention thus consists of providing a process for preparing vilazodone that is economically advantageous.
Another aim of the invention consists of providing a process for producing a synthesis intermediate of vilazodone without resorting to the use of vitride as reducing agent.